What's perfect alongside a big pack of Flesh Hounds of Khorne, when they've already have a Herald? (...or Chaos Lord, perhaps. I still havent been able to give Chaos: Khorne Daemonkin more than a cursory glance.)
A couple of Maulerfiends would extend the theme perfectly, I felt. I already have a Forge Fiend that I'm pretty much underwhelmed with. These two, on the other hand, can join the "Kennel Club" rush for my opponent's lines and add to the number of threats that have to be dealt with - sooner rather than later.
The idea is to enable my opponent to make the wrong choices during his turn. These two models, like their smaller cousins, can move fast enough to catch almost anything on the table.
Even though these guys really like to act like they're the biggest badest mofos in the valley, with some of the latest codex releases the facts of the matter is that they're a little over medium sized boys at best.
That means that I can't just throw these guys forward without regard for how intervening terrain will aid or hinder them or what the models directly across the table can to to them before they can get to where I want them. I'll still have to keep my wits about me to get the most out of these models too...